奥连特盆地白垩系海绿石成因类型及沉积地质意义

厄瓜多尔奥连特盆地白垩系Napo组UT段发育一套分布广泛的富含海绿石的硅质碎屑岩,针对海绿石的岩相、矿物学、地球化学及时空属性进行分析,可以揭示海绿石的组分、成熟度、形成及成因类型,结合地质约束有助于理解其形成的沉积地质意义.利用偏光显微镜、X射线衍射、电子探针及Qemscan对海绿石矿物的岩相、矿物组成和主量元素进行系统地分析.暗绿色、呈弯曲玫瑰花状的海绿石具有高的K₂O含量(平均值为8%,质量百分比),是形成于海相低沉积速率环境的高演化成熟型海绿石云母矿物或狭义范畴的海绿石.化学组分和时空属性揭示研究层段的海绿石经历了一定程度风暴流和/或潮汐流作用的搬运改造,属于层内准原地海绿石.UT段海绿石含量向上的增大趋势和成熟度的变化,以及横向上从盆地东部斜坡区埋深2~3 km到西部盆缘露头区相距约120 km的海绿石在形态和化学成分上具有相似性,指示其主要是层内准原地海绿石的特点.UT段垂向上海绿石含量增大的趋势同时反映外陆棚物源区原地海绿石向岸方向的短距离迁移,反映了相对海平面持续上升的海进过程;而且同时期海绿石平面上的广泛分布指示沉积时期的环境属于构造稳定的陆表海.      

徐州大北望寒武系徐庄组海绿石成因探讨

徐州大北望寒武系徐庄组发育不同类型海绿石，为探讨不同类型海绿石的成因，基于海绿石的矿物学、地球化学及沉积环境分析，利用偏光显微镜、X 射线衍射及电子探针等方法对各含海绿石岩层及不同类型海绿石进行系统对比研究查明海绿石的指相意义。结果表明，徐庄组发育颗粒状、碎屑假象状和胶团状三种类型海绿石，其中颗粒状海绿石具有中—高含量钾、高含量铁、砂岩中—高含量铝、石灰岩中低含量铝等特征；碎屑假象状海绿石具有变化大的钾、铁、铝，且保持着其母质形态特征；胶团状海绿石具有高钾、高铁、低铝特点。颗粒状海绿石成因符合颗粒绿化理论，砂岩中海绿石易受环境影响；碎屑假象状海绿石成因符合层状晶格理论及假象替代理论，受到交代和溶蚀作用，因受较强的水动力条件影响成分变化较大；胶团状海绿石是凝胶状海绿石通过胶结作用沉淀，形成于稳定环境中。     

海绿石的成因、指相作用及其年龄意义

海绿石以独特的绿色自生色和球粒形状与围岩形成明显反差,关于其成因、演化、沉积和地层学意义目前存在3种普遍被认可并被采用的观点：海绿石是典型的海相沉积自生矿物,原地海绿石是“慢速、弱还原、较深水环境”的典型指相矿物之一;通常是海侵相的产物,含海绿石的地层在浅海沉积中常被作为海侵时期“凝缩段”及其相关沉积的识别标志之一;是沉积年代学中K-Ar、⁴⁰Ar/³⁹Ar年龄理想的测定对象。在采用海绿石作为典型指相矿物的过程中,应注意海绿石可以形成于多种沉积环境中,只有原地海绿石才能作为海侵时期“凝缩段”及其相关沉积的识别标志;海绿石年龄往往呈“年轻化”或“老化”,没有火成岩定年准确,只有成熟、富钾的海绿石才是最好的定年对象。     

南海北部的海绿石

作者研究了南海北部表层沉积物中10个站位的海绿石。用显微镜、各种谱仪、透射电镜、扫描电镜、电子探针和化学分析等方法,对海绿石的外表特征及矿物学特性,进行了较为系统的分析;并结合海绿石的产状和分布,研究了它们的成因及沉积环境问题。本区海绿石可分为生物状海绿石、页状海绿石和颗粒状海绿石;根据X射线和红外光谱等特征,有混合层海绿石和混合物海绿石两类;根据化学成份计算黑色生物状海绿石的晶体化学     

对“指相矿物”海绿石的重新认识

长期以来，海绿石一直被认为是在特定海洋条件下形成的自生矿物，被作为海相标志，随着陆相海绿石的不断发现，有必要对这一观点进行重新认识。本文通过对不同地区、不同环境中的海绿石的统计研究认为：海绿石既可以形成于海洋环境，也可以形成于陆相湖泊环境，海绿石不能作为海洋环境的指相矿物；一般来说，形成于陆相湖泊环境的海绿石与形成于海洋环境的海绿石相比，在化学成分上具有Ａｌ２Ｏ３、Ｋ２Ｏ含量高而ＦｅＯ含量低的特点     

不同化学类型海绿石的形成模式

海绿石作为一种典型的海相形成物已为人们普遍承认。但是,关于海绿石的形成模式,特别是不同化学类型海绿石的形成模式,至今还很少有所报道。苏联学者卡扎科夫最近对高加索山前地区和大高加索北山坡亚普第一阿尔俾时期的早—中自垩世古盆地不同相带中的海绿石进行了系统的研究。根据研究结果,提出如下不同化学类型海绿石的形成模式: 铁以与有机物络     

泰康湖湾海绿石矿物学特征及其形成条件的探讨

近年来,在松辽盆地西部泰康湖湾下白垩统青山口组二、三段陆相地层中发现了海绿石(以下简称泰康海绿石)。本文在矿物学研究的基础上,讨论了该海绿石的形成条件和指相意义。     

陕南地区埃迪卡拉纪陡山沱组下部海绿石的成因机制：对古海水氧化还原条件的启示

海绿石是海洋环境中一类重要的自生矿物,在古环境研究方面具有广泛的应用。基于中国陕南地区埃迪卡拉纪陡山沱组下部海绿石的分布特征,对其开展了综合的岩相学、原位微区成分定量分析、X-射线衍射(XRD)分析等研究,旨在探讨海绿石的形成机制,剖析研究区埃迪卡拉纪早期的氧化还原环境。偏光显微镜和扫描电镜(SEM)观察结果表明,海绿石多以胶体沉淀物的形式充填于石英、长石等碎屑矿物颗粒之间的孔隙中,为早期成岩阶段自生沉淀成因。由于海绿石的形成需要Fe(Ⅱ)和Fe(Ⅲ)的同时存在,Fe氧化还原界面附近(次氧化)最有利于海绿石的发育,因此研究区陡山沱组下部海绿石的形成指示了次氧化的孔隙水条件。能谱(EDS)定量分析表明,研究区陡山沱组的海绿石具有高K₂O和Al₂O₃、低Fe₂O₃含量,该化学组分是前寒武纪海绿石的典型特征。碎屑矿物溶解及海水与孔隙水之间的物质交换提供了海绿石演化过程所需的元素。与贵州瓮安地区同时期的含海绿石地层相比,研究区海绿石的分布层位相对局限,表明古海水氧化还原环境和古地理环境...     

藏西南札达地区白垩系海绿石的成因及意义探讨

<正>海绿石是含水、富铁的云母类矿物,钾含量一般高于6%。通常认为,海绿石形成于海底沉积物与水的接触界面附近,与低的沉积物供应速率有关(Odinetal.,1981;Amorosi,1997;Huggettetal.,2010)。含海绿石地层以形成层序地层学中的凝缩层为特征,被认为与海进序列有关(Van     

天津蓟县中元古界铁岭组叠层石灰岩中原地海绿石的沉积学意义

天津蓟县剖面中元古界铁岭组二段叠层石灰岩中普遍发育海绿石。野外观察表明,海绿石主要分布在叠层石柱体间的泥晶灰岩中,呈薄膜状富集在叠层石鞘外缘;微观特征分析表明,海绿石呈不规则状的胶体形式,显示了原地海绿石的基本特点。电子探针的组分分析表明,铁岭组中的海绿石为中成熟度的海绿石。由于产在潮下高能柱状叠层石灰岩中,铁岭组中的海绿石并不反映低沉积速率或沉积间断的沉积条件,与现代海绿石的形成环境具有明显的差异。因此,中元古界铁岭组叠层石灰岩中的中成熟度原地海绿石是特殊沉积背景下的独特产物,为研究海绿石在地质历史时期产出的多样性提供了一个重要实例。     

东海西湖凹陷渐新统花港组海绿石的发现及其意义

在西湖凹陷渐新统花港组中首次发现非正常海相海绿石。可分为三种类型:即团粒状海绿石、胶结物海绿石和碎屑假象海绿石。前两者属沉积过程或成岩初期的产物。通过沉积学研究，结合微量元素及介质条件分析认为，花港组总体为滨岸湖泊三角洲－河流体系，但是曾程度不同地受到海水或咸水-半咸水影响。花港组的时代就可能归属为始新统。这一认识上的突破除了花港组年代地层的对比意义以外，还将引起对盆地演化阶段、沉积体系空间配置及油气有利相带预测等问题的重新认识。     

陕北三叠系上统延长油层中海绿石的发现及其初步研究

本文对陕北三叠系延长群延长油层中的海绿石——延长海绿石进行了分析研究。结果表明,延长海绿石的矿物学特征与一般海绿石相同,其扩展层含量19%,属于无序低钾云母型结构。碳同位素及微量元素分析表明,延长海绿石系陆相淡水-半咸水湖泊环境下的自生矿物,延长海绿石存在于湖泊三角洲前缘远沙坝或三角洲间湖湾的粉-细砂岩中,也常与自生黄铁矿共生,其形成时水深为50-100m。海绿石的存在指示着该处为弱还原环境,对于成油较为有利。因此,在陆相湖泊三角洲环境中,也应当建立海绿石地球化学相。     

Nature mineralogique et origine des glauconies du plateau continental du Gabon et du Congo

The detailed analysis of pellets deposited on the continental shelf off Congo and Gabon (Gulf of Guinea) reveals the present formation of goethite and berthierine-granules, as well as that of glauconite. The goethite is being formed in the most oxygenized zones, independently of the initial nature of the granular support and, sometimes, takes the form of pseudooolites. The berthierine is being formed in the Ogooue delta zone. To us the deltaic environment, rather than the temperature factor, seems determinant. Principally, this berthierine is found in the form of coprolites, of initial kaolinic composition. Incrustations of calcareous debris and fillings of animalculae tests are present. This genesis is recent (post-Flandrian) and is still continuing. The glauconite exists practically uniquely in the form of coprolites, from the medium-depth zones of the continental shelf (—50 m) down to the upper continental slope (—300 m). The sèdiment in which it was formed, and is probably still being formed, is older (ante-Flandrian). The actual rate of sedimention is null when glauconite is forming. The glauconite formation may be broken down into several stages, which are found at different sampling depths and, sometimes, in the same samples. The pellets are formed first. These original pellets, of kaolinic nature, gradually become smectitic. The evolution continues, becoming a component with diffractometric behaviour identical with that of an interlayered material (illite-vermiculite) with the illite dominant. Correlatively, the K₂O percentage increases from 2–3% in the smectites to 5–6% in the most evolved component. The mineralogical composition of these last pellets is identical with that of certain fossil glauconites, the evolution of which could be followed up to the best crystallized glauconite mineral. Thus, we were able to reconstitute the formation history of the glauconite from any mineralogical support up to the typical glauconite mineral (Table l). Two conditions necessary for this formation are detected here: the time factor, as has often been pointed out, is important. However, it is, above all, the environment factor which has attracted our attention. The forming of pellets favours and determines the geo-chemical evolution through the creation of a semi-confined environment. Reactions take place there in a more concentrated environment than in the open sea, this environment is characterized by a large surface of reaction, since the granule is porous. Sedimentologically, it is possible to distinguish two groups of glauconites: one, monomineral, corresponds to more or less crystallized glauconite mineral; the other, plurimineral, consists of various TOT minerals. Only the first has the significance generally attributed to all glauconites : open epicontinental marine environment, free of sedimentation for a long time. The various cases of evolution encountered here are summarized below (Table 1).     

内蒙古西乌珠穆沁旗阿木山组海绿石的特征及其沉积环境

在内蒙古西乌珠穆沁旗晚石炭世—早二叠世阿木山组第三段泥晶灰岩中发现有海绿石。对海绿石的微观特征分析表明,阿木山组海绿石呈团粒状结构,同时呈胶体产出于方解石周边,显示了原生海绿石的基本特点。电子探针的组分分析表明,阿木山组中的海绿石为高成熟度的海绿石。通过对不同地区和不同环境下海绿石的组分特征分析,建立了一种海绿石沉积的理想模式,同时揭示了阿木山组第三段海绿石化作用是在含氧量不够充分的弱还原状态下的正常浅海中进行的。本区阿木山组的下碎屑岩段和上灰岩段是在海水两进两退环境下的沉积,阿木山组灰岩中发现的海绿石则有可能代表了一个海进的开始。本区海绿石的发现及研究,对于进一步研究该区层序地层特征、地层格架及区域地层对比具有重要意义。     

Origin of glauconite in the recent bottom sediments of the ocean

There are two general types of sedimentary glauconite in Recent ocean sediments: terrigenous-allogenic and authigenic glauconite. Recent sediments of the oceans contain mainly terrigenous-allogenic glauconite (shelf and continental slope) which is formed from ancient glauconite-bearing rocks on coasts, islands and the ocean floor. The age of terrigenous-allogenic glauconite ranges from 2 to 70 m.y. (8 samples from the Atlantic Ocean, 13 from the Pacific Ocean, 1 from the Indian Ocean). The area of terrigenous-allogenic glauconite distribution correlates very well with the area of distribution of glauconite-bearing rocks on land and does not correlate with the climate and bathymetry.Authigenic glauconite is seldom found in Recent ocean sediments. The sediments with authigenic glauconite form transition zones between sediments with organic carbon, H₂S and sulphide near coasts and oxidized sediments of the ocean floor (red clay and others). The areas of authigenic glauconite distribution are not yet well known. The formation of authigenic glauconite occurs mainly during diagenesis of sediments by synthesis from interstitial solutions and/or alteration of clay minerals.     

Früher Kalzitzement in skandinavischen Orthocerenkalken: Beziehungen zum Glaukonit

Interrelations between glauconite and calcite cement are added to different indicators of preservation of early diagenetic phenomena in Lower Ordovician limestones of Sweden. The interrelations briefly discussed are, 1. glauconite postdating calcite cement in an early fracture filling, 2. glauconite postdating and coeval with calcite cement in the central cavity of sponge spicules, 3. glauconite intergrown with calcite single crystals, 4. calcite cement grown pari passu with shrinkage of glauconite grains, 5. relics of (resedimented?) calcite cement enclosed in glauconitic hardground crusts, 6. calcite cement enclosed in slumped massive glauconitite.     

Glauconitization of detrital silica substrates in the Barton Formation (upper Eocene) of the Hampshire Basin, southern England

Upper Eocene detrital silica grains (chert and quartz) of the Hampshire Basin display alteration and replacement fabrics by glauconite. Silica grains have etched surfaces due to glauconitization which appear green in reflected light and thin section. Quartz grains were glauconitized by surface nucleation and replacement, which spreads from the margin with progressive glauconitization, replacing the quartz grain interior. Chert grains were glauconitized by surface replacement and nucleation internally along cracks and in pores. Different forms of glauconite are associated with the two minerals; glauconite associated with quartz is generally highly-evolved whereas glauconite associated with chert is of the evolved variety. This is interpreted as being due to different surface-reaction control mechanisms associated with the two forms of silica. There is no evidence to suggest that glauconite evolved in stages from a nascent form. Two crystalline morphological forms of glauconite are found associated with both quartz and chert. Glauconite growing within a confined space has a laminated morphology whilst glauconite occurring on the surface has a rosette morphology.     

Glauconite

The term glauconite has been employed in two senses. It has been used most commonly as a morphological term for sand-sized greenish grains found in sedimentary rocks, but also as a name for a specific mineral species, a hydrated iron-rich micaceous clay mineral. The two uses are not synonymous, since not all morphological glauconite consists exclusively of mineral glauconite, nor is the latter restricted in its occurrence to such pellets. Mineral glauconite in sensu lato is a random interstratification of nonexpanding 10A?layers and expanding montmorillonitic layers. The amount of expandable layers may be over 50 % but it is customary to restrict the name mineral glauconite in sensu stricto to varieties with less than 10 % expandable layers. The variation in amount of expandable layers explains many of the observed variations in the properties of glauconite including chemical composition (especially potassium content), thermal characteristics, cation exchange capacity, colour, refractive index and specific gravity. Mineral glauconite is believed to form by the progressive absorption of potassium and iron by a degraded layer silicate lattice of low lattice charge and elimination of other silicate-lattice types under suitable environmental conditions, of which the most critical seems to be the redox potential. The catalytic activity of marine organisms is no longer thought to be essential, although decaying organic matter and empty foraminiferal tests supply the ideal environment for glauconite genesis. The process of glauconitization is arrested by rapid sedimentation, so that there is a relationship between the variety of mineral glauconite formed and the nature of the host rock. Glauconite is found associated particularly with marine transgressions. Morphological glauconite grains are believed to form as casts, faecal pellets or by accretionary growth, but may have their morphology modified by subsequent re-working. A number of characteristic internal and external morphologies have been recognised. The wide range of environmental conditions suitable for its formation and its common detrital occurrence debars the use of glauconite in palaeo-environmental studies. Its major use in geology is for the absolute age dating of sedimentary rocks by the K-Ar method. Glauconitic deposits have no present day commercial value, but soils formed on glauconitic parent materials are notable for their fertility. Glauconite weathers by loss of potassium to produce a montmorillonitic or vermiculitic product with the release of, or oxidation of, structural iron, so that the grain has the appearance of having weathered to limonite.     

佳木斯地块金矿石英的热释发光与含金性

乌拉嘎、平顶山、老柞山金矿是佳木斯地块三个重要的金矿。研究表明，石英是金矿中重要的脉石矿物，也是金的主要载体。ＳｉＯ２含量低于９８％，而∑（Ａｌ２Ｏ３＋Ｋ２Ｏ＋Ｎａ２Ｏ）含量高于１．３％的石英为含金石英；含金或富含金石英的热释发光谱以双峰或多峰为其主要特征。因此，上述石英的标型特征可作为金矿床重要的找矿标志，对佳木斯地块的矿点评价和扩大找矿远景有着重要的意义